Two central aminergic model systems in which neurotoxin treatment appears to induce axonal remodelling will be studied in parallel. The bulbospinal monoamine system will be used to study (a) 5-HT and NE terminals in the spinal cord, (b) the question of synaptic connections being formed by new sprouts in the transected spinal cord. Hypothesized enhancement substances will be tested for their ability to promote growth of aminergic axons across the transection site. A combination of biostructure (EM; FM; morphometrics; adenylate cyclase histochemistry; HRP) and biochemistry (assays for cAMP, NE, 5-HT) will be used, with anticipation of neurophysiological and tissue culture correlations as later experimental stages warrant. This broad interdisciplinary approach is expected to provide related and converging data to help in understanding the process of central and peripheral adrenergic plasticity.